1. Field of the Invention
The present invention relates to ophthalmic lenses, and more particularly to contact lenses incorporating clearly identifiable, highly visible inversion marking(s) that become invisible when inserted or positioned on the eye.
2. Discussion of the Related Art
Myopia or nearsightedness is an optical or refractive defect of the eye wherein rays of light from an image focus to a point before they reach the retina. Myopia generally occurs because the eyeball or globe is too long or the cornea is too steep. A minus or negative powered spherical lens may be utilized to correct myopia. Hyperopia or farsightedness is an optical or refractive defect of the eye wherein rays of light from an image focus to a point after they reach or behind the retina. Hyperopia generally occurs because the eyeball or globe is too short or the cornea is too flat. A plus or positive powered spherical lens may be utilized to correct hyperopia. Astigmatism is an optical or refractive defect in which an individual's vision is blurred due to the inability of the eye to focus a point object into a focused image on the retina. Astigmatism is caused by an abnormal curvature of the cornea. A perfect cornea is spherical whereas in an individual with astigmatism, the cornea is not spherical. In other words, the cornea is actually more curved or steeper in one direction than another, thereby causing an image to be stretched out rather than focused to a point. A cylindrical lens rather than a spherical lens may be utilized to resolve astigmatism.
Contact lenses may be utilized to correct myopia, hyperopia, astigmatism as well as other visual acuity defects. Contact lenses may also be utilized to enhance the natural appearance of the wearer's eyes. Contact lenses or contacts are simply lenses placed on the eye. Contact lenses are considered medical devices and may be worn to correct vision and/or for cosmetic or other therapeutic reasons. Contact lenses have been utilized commercially to improve vision since the 1950s. Early contact lenses were made or fabricated from hard materials, were relatively expensive and fragile. In addition, these early contact lenses were fabricated from materials that did not allow sufficient oxygen transmission through the contact lens to the conjunctiva and cornea which potentially could cause a number of adverse clinical effects. Although these contact lenses are still utilized, they are not suitable for all patients due to their poor initial comfort. Later developments in the field gave rise to soft contact lenses, based upon hydrogels, which are extremely popular and widely utilized today. Specifically, silicone hydrogel contact lenses that are available today combine the benefit of silicone, which has extremely high oxygen permeability, with the proven comfort and clinical performance of hydrogels. Essentially, these silicone hydrogel based contact lenses have higher oxygen permeabilities and are generally more comfortable to wear than the contact lenses made of the earlier hard materials.
Contact lenses need to be thin and flexible for wearer comfort. Such flexibility may result in contact lens inversion upon handling. Essentially, contact lens inversion occurs when the corneal or back curve side of the contact lens inverts and becomes the front curve side of the lens due to handling in some manner. Accordingly, if the contact lens is placed on the eye in an inverted state, the desired vision correction and comfort are not achieved. Thus, there is a need for marking the contact lenses such that their normal state may be easily distinguished from the inverted state. In order not to affect the aesthetic and optical properties of the contact lens, the currently utilized inversion marking is preferably made in the form of a small number series positioned at the periphery of the contact lens. This makes the marking barely visible thereby requiring special effort and adequate illumination to locate and identify it. Accordingly, there exists a need for an inversion marking, which may include multiple symbols and/or characters, which are highly visible and easily identifiable when the contact lens is out of the eye, but disappears or is optically invisible when placed on the eye.